It is known to make pantyhose articles by suitably cutting two stockings lengthwise from the open end, that is, from the elastic hem of the bodice, to a point spaced a predetermined distance from the garter line which separates the bodice from the leg and, afterwards, by sewing together the juxtaposed edges of the thus cut stockings. To this end, the two stockings to be sewn to form a pantyhose article are first fitted on two binate or paired juxtaposed shapes, then they are lined up vertically and brought close to each other, so as to provide a correspondence between the elastic hem and the garter lines thereof.
Owing to the above mentioned correspondence, the longitudinal cut leads to the definition of two edges of equal length and equally located with respect to the garter line. In a successive step, the juxtaposed edges of the two stockings are sewn together to form a pantyhose article: the seams being carried out throughout the length of the edges.
It thus follows that in order to carry out the cut with the necessary accuracy, the garter line must be distinctly sensed.
Devices are known to overcome this problem for detecting the garter on a stocking, and these devices are provided with optical sensors able to sense the difference of consistency between the fabric of the stocking leg and that of the bodice.
But, for the sensors to distinctly detect the garter line it is necessary to dispose the stocking in stretched attitude in a correspondence with the sensors, that is, with the stockings in a wrinkle-free condition.
A device is known from the Japanese Patent No. 1-312.410 for positioning the stockings in a pantyhose-making machine. This device is provided with first optical sensors to detect the presence of the stockings over the relevant paired shapes, and these first sensors are associated with means for longitudinally sliding the stockings over the shapes.
Second optical sensors are used for sensing the garter line of the thus disposed stockings. These second sensors are associated which means for transferring the garter lines to a predetermined position over the shapes.
Third optical sensors for sensing the elastic edge of the stockings and these third sensors are associated with means for transferring the stockings to a predetermined position over the shapes.
The operation of this known device may be described as follows.
The two stockings to be combined to obtain a pantyhose article are fitted in bulk over the two paired shapes. As soon as the sensors for the detection of the stockings sense the presence thereof, the means for positioning the elastic hems take over the latter and put them thoroughly onto the shapes, as far as the stocking regions with the garter line result fitted on the shapes and allow the detection thereof by the corresponding sensors. Thereafter, means associated to the sensors provide for aligning the two garter lines. Finally, the sensors for detecting the elastic hem of the stockings move forward to a predetermined alignment position, and the associated means for positioning the elastic hems provide for the transfer thereof up to the alignment position. At this point, the stocking bodices are stretched wrinkle-free over a predetermined length and with the elastic hems and garter lines lined up vertically in order to properly carry out the subsequent cutting operation.
Yet, this known positioning device exhibits some drawbacks, the major of which being the need of moving the elastic hem and the leg of each stocking in two distinct steps and by means of different positioning members which must operate separately. This implies a higher constructional complexity of the machine, which is detrimental to the economy of production and running of the latter. Moreover, owing to the constructional complexity of the known device, the reliability of the machine provided with such device is heavily reduced, which brings about more frequent service interventions and longer dwell or down times. A further drawback is that the whole time necessary to make a pantyhose article is heavily affected by the speed at which the operations for positioning the stockings over the relevant shapes are carried out. When the making of a pantyhose article is to be sped up as much as possible--and considering that it is not possible at present to reduce the stockings-cutting and sewing times any further--it is impossible to attain very close tolerance limits in the detection of the garter lines, which implies inaccuracies in the pantyhose formation.